1. Field of the Invention
This invention relates to fluid handling processes and apparatus. More particularly, this invention relates to methods and apparatus for effecting controlled dispersal of fluid to achieve specific flow patterns. Such flow patterns are of interest in a wide range of applications (e.g., shower and sink sprays, spas that provide fluid massaging actions, drying equipment).
2. Description of the Related Art
Fluidic oscillators are well known in the prior art for their ability to provide a wide range of liquid spray patterns by cyclically deflecting a liquid jet. Examples of fluidic oscillators may be found in many patents, including U.S. Pat. Nos. 3,185,166 (Horton and Bowles), 3,563,462 (Bauer), 4,052,002 (Stouffer and Bray), 4,151,955 (Stouffer), 4,157,161 (Bauer), 4,231,519 (Stouffer), which was reissued as RE 33,158, 4,508,267 (Stouffer), 5,035,361 (Stouffer), 5,213,269 (Srinath), 5,971,301 (Stouffer), 6,186,409 (Srinath) and 6,253,782 (Raghu). The technology disclosed is these patents is summarized below.
However, before reviewing these patents, it is perhaps informative to make note of some of the distinct features of fluidic oscillators. The operation of most fluidic oscillators is usually characterized by the cyclic deflection of a fluid jet without the use of mechanical moving parts. Consequently, an advantage of fluidic oscillators is that they are not subject to the wear and tear which adversely affects the reliability and operation of pneumatic oscillators and reciprocating nozzles.
The fluidic oscillators described in U.S. Pat. No. 3,185,166 (Horton and Bowles) are characterized by the use of boundary layer attachment (i.e., the xe2x80x9cCoanda effect,xe2x80x9d which is named after Henri Coanda who was the first to explain the tendency for a jet issuing from an orifice to defect from its normal path so as to attach to a nearby sidewall) and the use of downstream feedback passages which serve to cause the jet issuing from a power nozzle to oscillate between exiting in either the right or left side ports. See FIG. 1 which shows the top view of a two dimensional fluidic which, as is conventional in fluidic technology, is assumed to have a transparent top surface so as to reveal the internal geometry of the fluidic.
This fluidic is symmetric about its longitudinal centerline Lxe2x80x94L and consists of an interaction region with sidewalls which diverge downstream from a power nozzle. A jet issued by the power nozzle is cyclically deflected back and forth between the interaction region sidewalls by a portion of the jet which is captured at a feedback passage inlet and fed back to effect deflection.
The feedback force exerted by the feedback passages must not only be sufficient to deflect the jet itself, but it must also overcome the boundary layer attachment of the jet to a sidewall. The result is that the oscillator cannot operate at jet pressures below a rather significant pressure level. Moreover, the attachment of the jet to the sidewalls during each half cycle of oscillation results in a xe2x80x9cdwellxe2x80x9d time wherein the jet is effectively stationary. The spray pattern produced by the cyclically deflected jet, which alternately exits through one or the other of the exit ports at the top of the oscillator, consequently contains greater concentrations of jet fluid at those pattern locations corresponding to the effective stationary state of the jet (i.e., the outer edges of the spray distribution pattern), rather than at other locations. It is therefore not possible to control pattern distribution or to achieve uniformly distributed patterns, with oscillators of this type. Furthermore, the use of porous plugs in the control tubes were seen to result in even longer duration jet xe2x80x9cdwellxe2x80x9d times on the sidewalls.
It should be recognized that the three-dimensional character of the flow from such fluidics can take a variety of forms depending upon the three-dimensional shape of the fluidic. For example, if the depth of the fluidic shown in FIG. 1 is approximately the same as the width of its exit ports, then an approximate, oscillating round jet with be sprayed from the fluidic. If the depth of the fluidic is much greater than the width of the exit port, then an oscillating, sheet of fluid will exit from the fluidic. If the fluidic is such that it has angular symmetry about its centerline, it""s exit port will be annular in shape and from it will spray an oscillating, annular ring of fluid.
The fluidic oscillators described in U.S. Pat. No. 3,563,462 (Bauer) are characterized by what is sometimes called a flow-reversing, interaction region which results in the flow from this fluidic""s power nozzle to have a bistable flow pattern. The use of downstream feedback passages, which connect at points downstream from the fluidic""s power nozzle, serves to cause the flow to oscillate between exiting from the right and left side ports. See FIG. 2. The sidewalls of the flow-reversing interaction region first diverge from the power nozzle and then converge toward an outlet throat in a downstream direction. When the jet flows along the left sidewall it is re-directed thereby toward the right as it egresses through the outlet throat; likewise, the right sidewall re-directs the jet toward the left. The entry of ambient fluid into the interaction region via the outlet throat is relatively restricted as compared to the Horton and Bowles oscillator, primarily because the outlet throat is narrower relative to the egressing jet than the downstream end of the Horton and Bowles oscillator. The limitation of ambient fluid entry reduces the boundary layer attachment to the interaction region sidewalls so that less feedback force is required to deflect the jet. Oscillation in the flow-reversing configuration is therefore possible at lower jet pressures than in the Horton and Bowles oscillator. When a liquid issues from the power nozzle into an ambient air environment, such oscillators with flow-reversing interaction regions display relatively low frequency oscilliations and have found numerous practical applications, such as in shower heads, lawn sprinklers, decorative fountains, industrial control equipments, etc.
The spray pattern produced by this type of oscillator is often nonuniform due to ambient air being ingested through the feedback passages and randomly mixed with issuing primary jet liquid. In addition, since a mixture of air and liquid has a different viscosity than the liquid alone, and since the size of the droplets exiting from this type of oscillator are a function of the viscosity of the resulting fluid spray, the sprays from these oscillators are often found to have considerable variability in droplet sizes.
The fluidic oscillators described in U.S. Pat. No. 4,052,002 (Stouffer and Bray) are characterized by the selection of the dimensions of the fluidic such that no ambient fluid or primary jet fluid is ingested back into the fluidic""s interaction region. See FIGS. 3(a)-3(b). This yields a spray pattern that is more uniform and with a spray that is made up of droplets of more uniform size.
The absence of inflow or ingestion from outlet region is achieved by creating a static pressure at the upstream end of interaction region which is higher than the static pressure in outlet region. This pressure difference is created by a combination of factors, including: the width T of the exhaust throat is only slightly wider than power nozzle so that the egressing power jet fully seals interaction region from outlet region; and the length D of interaction region from power nozzle to throat, which length is significantly shorter than in prior art oscillators. It should be noted that the width X of control passages is smaller than the power nozzle. If the width of power nozzle at its narrowest point is W, then the following relationships were found to be suitable, although not necessarily exclusive, for operation in the manner described: T=1.1-2.5 W and D=4-9 W, with the ratios of these dimensions also being found to control the fan angle over which the fluid is sprayed.
The oscillator frequency was found to depend upon the size of the oscillator and other factors. Generally, the frequency f, in Hertz, may be represented by: f=54.4 p1/2, where p is the liquid pressure, in psi, applied to the oscillator over the range of 1-160 psi.
By adding a divider in this fluidic""s outlet region, it becomes what can be referred to as two-outlet oscillator of the type that might be used in a windshield washer system. See FIG. 4 and U.S. Pat. No. 4,157,161 to Bauer.
The oscillators described in U.S. Pat. No. 4,151,955 (Stouffer) are quite different from the prior oscillators described above in that they do not depend upon boundary layer attachment fluid flow phenomena. Instead, the oscillators in U.S. Pat. No. 4,151,955 are characterized by their use of a fluid phenomena known as a xe2x80x9cKarman vortex streetxe2x80x9d for dispersing fluid. This oscillator consists of an inlet from which a fluid stream issues in the direction of a downstream island or obstacle which is just before the chamber""s outlet opening. See FIG. 5(a). As the fluid stream impinges upon the obstacle, a vortex street is established behind the obstacle.
Upon issuing from the outlet, the stream is cyclically swept back and forth by the vortex street. Depending upon a number of factors, including the area of the outlet and the position of the obstacle relative to the outlet, the issued stream can be either a swept jet or a swept fluid sheet, the sheet being disposed generally perpendicular to the plane of the device and being swept in the plane of the device. See FIG. 5(b). Similarly, like other fluidics, this fluidic can be configured such that its three-dimensional form has angular symmetry about its centerline. See FIG. 5(c) which shows this type of fluidic being used in a shower head. See also U.S. Pat. No. 5,035,361 (Stouffer), which is a continuation-in-part of U.S. Pat. No. 4,151,955, for more illustrations of the various oscillator geometries that may be used with this type of fluidic oscillator.
In the case of the swept jet, the sweeping action causes breakup of the jet into uniformly sized and distributed droplets. In the case of the swept sheet, smaller droplets are formed due to the mutual interaction between two portions of a jet within the region of the device downstream of the obstacle.
The fluidic oscillators described in U.S. Pat. No. 4,231,519 (Stouffer), which was reissued as U.S. Pat. No. RE 33,158, are also quite different from the prior art in that they employ yet another fluid flow phenomena to yield an oscillating fluid output. The oscillators of U.S. Pat. No. 4,231,519 are characterized by their utilization of the phenomena of vortex generation, within an expansion chamber prior to the fluidic""s throat, as a means for dispersing fluid. FIG. 6(a) shows the general configuration of such a fluidic oscillator. It comprises a jet inlet that empties into an expansion chamber which has an outlet throat at its downstream end. It also has an interconnection passage that allows fluid to flow from one side to the other of the areas surrounding the jet""s inlet into its expansion chamber. FIGS. 6(b) and 6(c) show other similar fluidics that have alternate forms for the geometry of their expansion chambers. Additionally, the interconnection passages lie wholly in the plane of the fluidic, rather than above it as shown in FIG. 6(a). Note that the interconnection passage shown in FIG. 6(c) is of variable volume. This proves to be useful in controlling the frequency of the oscillating flow from this fluidic.
The general nature of the flow in such fluidics is illustrated in FIG. 6(d). Vortices are seen to be formed near the throat. As these grow in size they cause the centerline of the fluid flowing through the expansion chamber to be deflected to one side or the other such that the fan angle, xcex8, of the jet issuing from the throat ranges from approximately +45 degrees to xe2x88x9245 degrees. The result of these flow oscillations is a complicated spray pattern which at a given instant takes a form similar to that shown in FIG. 6(e).
The uniformity of the sprays from fluidic oscillators such as that shown in FIG. 3(a) have been further improved upon, according to U.S. Pat. No. 4,508,267 (Stouffer), by further utilizing this phenomena of vortex generation within the fluidic itself, see FIG. 7(a). This was reportedly necessary because it was found that prior oscillators tended to have higher spray concentrations at each end of the fans over which the sprays were spread. This phenomena was due to flow in the fluidic""s interaction region tending to dwell on the respective sidewalls until the pressure gradient at the power nozzle caused the flow to switch from one sidewall to another.
The fluidic oscillator of FIG. 7(a) is characterized by having sidewalls which are laterally remote from the power nozzle exit and protuberances at the ends of these sidewalls. Thus, the interaction region of these oscillators is not the streamlined, diverging/converging cross sections of prior oscillators, but a more box-like shape having protuberances on the downstream end of the laterally remote sidewalls.
The key transitory, flow patterns from and within this fluidic are shown in FIG. 7(b). We no longer have boundary layer, wall attachment flow phenomena, but instead have vortexes alternately being formed on either side and just downstream of the power nozzle exit. As these vortices are swept downstream they deflect the jet""s direction of flow such that the jet exits the fluidic""s throat with its direction oscillating from being plus a certain fan angle, xcfx86, from the jet""s longitudinal centerline to being minus this same fan angle from the centerline.
The fluidic oscillators disclosed in U.S. Pat. Nos. 5,213,269 (Srinath) and 5,971,301 (Stouffer) are referred to as xe2x80x9cbox oscillatorsxe2x80x9d having interconnects which serve to help control the oscillating dynamics of the flow that exits from the fluidic""s throat. For example, the effect of these interconnects, assuming that they are appropriately dimensioned relative to the other geometry of the fluidic, is generally seen to be about a doubling of the fan angle of the fluid exiting from the fluidic""s throat. FIG. 8(a) from U.S. Pat. No. 5,213,269 shows an embodiment in which the interconnect takes the form of passage that connects points on opposite side of the fluid""s throat. FIG. 8(b) from U.S. Pat. No. 5,971,301 shows an embodiment in which the interconnect takes the form of a slot in the bottom wall of the fluidic""s interaction region.
U.S. Pat. No. 6,253,782 (Raghu) discloses a fluidic oscillator of the type that provides a shaped interaction region having two a pair of entering power nozzles and a single throat through which the resulting fluid flow exits the fluidic oscillator. See FIGS. 9(a)-(b). The jets from the power nozzles are situated so that they interact to form various vortices which continually change their positions and strengths so as to produce a sweeping action of the fluid jet that exits the throat of the fluidic. In a preferred embodiment, the interaction region has a mushroom or dome-shaped outer wall in which are situated the power nozzles.
U.S. Pat. No. 6,186,409 (Srinath) discloses a fluidic oscillator which has two power jets entering a fluid interaction region from the opposite sides of its longitudinal centerline. See FIG. 10. These jets are fed from the same fluid source, and are unique because they employ a filter between the jet source and the upstream power nozzles to remove any possible contaminants in the fluid.
Despite much prior art relating to fluidic oscillators, there still exists a need for further technological improvements in this area. For example, new fluidic oscillators are needed that can provide controllable sprays of droplets that prove to be more beneficial in assorted commercial applications, such as surface cleaning tasks. Additionally, greater tactile pleasure is always desired from the sprays that emanate from shower heads.
There has been summarized above, rather broadly, the prior art that is related to the present invention in order that the context of the present invention may be better understood and appreciated. In this regard, it is instructive to also consider the objects and advantages of the present invention.
It is an object of the present invention to provide new, improved fluidic oscillators and fluid flow methods that are capable of generating oscillating, fluid jets having very distinctive and controllable flow patterns.
It is another object of the present invention to provide improved fluidic oscillators and fluid flow methods that yield fluid jets having unique properties that prove to be beneficial in a number of commercial applications.
It is yet another object of the present invention to provide improved fluidic oscillators and fluid flow methods that yield fluid jets and sprays of droplets having properties that make them more efficient for surface cleaning applications.
It is still another object of the present invention to provide improved fluidic oscillators and fluid flow methods that yield fluid jets and sprays of droplets having properties that make them more pleasurable to use in various human showering activities.
These and other objects and advantages of the present invention will become readily apparent as the invention is better understood by reference to the accompanying summary, drawings and the detailed description that follows.
Recognizing the need for the development of improved fluidic oscillators that are capable of providing a broader variety of spray patterns having controllable liquid droplet shapes, the present invention is generally directed to satisfying the needs set forth above and overcoming the disadvantages identified with prior art devices and methods.
In accordance with the present invention, the foregoing need can be satisfied by providing a fluidic oscillator that in a preferred embodiment is comprised of the following elements: (1) a switching chamber having an inlet port that allows a pressurized liquid to enter and flow through the oscillator, (2) an exhaust passage having a sidewall that forms one boundary wall of the switching chamber, (3) a container passage having a sidewall that forms the second boundary wall of the switching chamber, (4) an expandable, gas-filled container connected to the distal end of the container passage, and (5) an expansion chamber connected to the distal end of the exhaust passage, with the expansion chamber having an exhaust orifice that allows liquid to flow from the oscillator. In operation, such an oscillator yields a liquid jet that issues from the inlet port into the switching chamber and alternately tries to switch its flow direction between the container and exhaust passages. This switching action serves to generate a controllable series of pressure waves in the exhaust passage and expansion chamber which act to control the pattern of the liquid that flows from the orifice.
In another preferred embodiment, the present invention takes the form of a method for providing a free fluid jet from fluid under pressure, with the jet having distinctive, controllable and useful flow patterns. The steps in this method include: (1) forming a contained fluid jet, (2) deflecting the contained jet between an exhaust passage and a container passage, (3) providing the exhaust passage at its distal end with an expansion chamber, with this chamber having an orifice that allows the fluid to flow from the chamber, (4) providing the container passage at its distal end with a container, wherein the container and its contents work together to provide this distal end with specified compliance capabilities, and (5) generating controlled pressure waves in the exhaust passage and expansion chamber as a result of these jet deflections, with the pressure waves acting to control the pattern of the fluid jet that flows from the orifice.
Thus, there has been summarized above, rather broadly, the present invention in order that the detailed description that follows may be better understood and appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of any eventual claims to this invention.